In recent years battery powered portable electronic equipment has been rapidly growing in popularity. A great deal of such equipment is used for gathering, storing and processing information. The information must first be sensed then processed, and stored for future use. Equipment such as barcode readers, portable computers, medical equipment and electro-optical equipment are but a few examples. Cordless electronic power tools are also in great demand because of the great convenience they afford.
Electronic equipment such as, for example, laser scanning barcode readers, contain miniature precision optical components such as mirrors, lenses, optical filters and high sensitivity electronic circuits. Any moisture, condensation, or small particulate material such as smoke or dust can fog and degrade the optics as well as internal electronics when used in outdoor or industrial environments if the equipment housing is not well sealed.
In designing portable electronic equipment, two major considerations include how such portable equipment is packaged and how it is turned on and off in order to operate it. An external switch mounted on the housing of the equipment is the usual method of turning the equipment on and off. This solution, however, leads to many other problems and high cost as will be shown.
External mechanical switches require force to operate and lead to operator fatigue. Openings in the equipment housings are required to link the external mechanical parts of the switch mechanisms to the equipment inside of the housing thus leading to additional drawbacks that relate to sealing of the housing. Sealing portable equipment for durability in harsh outdoor environments adds additional expense, raises the parts count, introduces complexity and reduces equipment reliability. The mechanical linkages needed to actuate traditional external mechanical switch mechanisms coupled with internal electromechanical switch mechanisms themselves can wear out, freeze up, break, bind, become unreliable when moisture or dirt gets into them and so on leading to a wide variety of failures.
The housings of portable electronic equipment are commonly made from plastic moldings and incorporate openings into such moldings to accommodate external switch mechanisms, thereby increasing tooling costs.
Thus, it is desirable for such portable equipment to have certain general characteristics. Among these are low power drain and short operation cycle time for long battery life, ease of actuation, ease of operation to minimize operator fatigue, durability especially for use in harsh and outdoor environments and of course low cost. The switch mechanisms used to operate such equipment can greatly influence the quality of these characteristics.